Wind turbines normally comprise one or more energy generating units, each energy generating unit comprising a hub carrying one or more wind turbine blades. The wind acts on the wind turbine blades, thereby causing the hub to rotate. The rotational movements of the hub are transferred to a generator, either via a gear arrangement or directly, in the case that the wind turbine is of a so-called direct drive type. In the generator, electrical energy is generated, which may be supplied to a power grid.
Some wind turbines are provided with two or more energy generating units in order to increase the total power produced by the wind turbine, without having to provide the wind turbine with one very large, and therefore heavy, energy generating unit. Such wind turbines are sometimes referred to as ‘multirotor wind turbines’.
In multirotor wind turbines the energy generating units may be carried by a load carrying structure which is, in turn, connected to a tower structure. Thereby at least some of the energy generating units are not mounted directly on the tower structure, and they may have a centre of gravity which is displaced with respect to a longitudinal axis defined by the tower structure. When the wind acts on energy generating units mounted in this manner, thrust forces will be created, which will in turn cause loads to be introduced in the load carrying structure, and possibly at connection points between the load carrying structure and the tower structure.
GB 2443886 B discloses a multirotor wind turbine comprising a tower to the top of which a cross-beam structure is mounted by means of a yaw bearing and pivoting connection. The cross-beam structure carries two or more electricity generating turbine rotors mounted at the extremities. The cross-beam may be supported by stays attached to a central column.
DE 10 2012 020 052 B3 discloses a wind turbine with a foundation, a tower and at least one nacelle with a rotor on the tower. The tower is provided with a bearing with an inner part mounted on the tower and an outer part. Two arms are mounted pivotally to the outer bearing part at opposite sides, and the arms carry the nacelles. The arms may be moved pivotally by means of wires attached to the arms and to the tower.